This invention relates to door closers of the kind including a housing for mounting within the thickness of a door, spring means within the housing and acting on a tension member which extends outwardly from the housing and is coupled to an anchor member for securing to a door frame at a position adjacent to said housing, in use said spring means acting to draw the housing and the anchor member together thereby closing the door relative to the door frame.
For examples of such door closers reference may be made to British patent specification No. 1044911. In the construction disclosed therein, the tension member includes an outer end portion which is in the form of an articulated chain. The use of such a chain has the advantage that it is mechanically simple and yet allows the door to swing through substantially 180.degree. providing the chain length is sufficient.
In other constructions, as for example described in British patent specification No. 1263214, the tension member includes a rigid linkage, but this has the disadvantage that the geometry of the linkage system usually imposes a significant restriction on the angle through which the door can swing, and for this reason a flexible member is to be preferred. In practice, such a flexible member, has so far as we are aware, always been formed as a chain of some kind, having a finite number of links.
In general, this is satisfactory as such chains are readily available, but we have found that under some circumstances the chains conventionally used can have two disadvantages. Firstly, it has been customary to employ chains in which the links are articulated and are flexible in only one plane. Closers employing such chains cannot therefore be used on doors with rising butt hinges, and the anchor member needs to be quite accurately aligned with the housing when the closer is fitted. Moreover, if the door drops over an extended period of use, the chain may jam due to its lack of flexibility in a vertical plane.
Secondly, the length of such a chain is not infinitely variable, since it can only comprise an integral number of links.
In designs of the type described in British patent specification No. 1044911, the tension member has at its innermost end an adjustable connection with a component against which the spring means acts to draw the tension member into the housing. Adjustment of this connection enables the force exerted by the spring to be varied. Thus, the effort required by the user when opening the door from its closed position can be regulated, or the force exerted by the spring can be adjusted to suit the weight of the door. However, since the chain connected to the anchor member is of a predetermined length, alteration of the spring setting may restrict the degree to which the door can be opened, this being resisted by compression of the spring to the extent that adjacent turns of the coil come into contact.
In general terms the present invention involves in the use of a tension member in which at least an outer end portion comprises a flexible cable which terminates in an abutment engaging behind the anchor member, the cable having a collar fixedly secured thereto at a position spaced from said abutment member, a suitable tool enables the cable to be rotated about its center line to effect adjustment whereby engagement of a spacer member between said collar and said housing prevents the anchor member being drawn up to the housing so as to facilitate installation of the door closer or prevent closure of the door when so required after installation.